| At present,non-contact temperature measurement has become the mainstream measurement method of temperature measurement in the furnace with its advantages of high visualization and real-time online monitoring.However,due to the existence of carbon ash particles in the high temperature flue gas in the furnace and the limitations of its own temperature field reconstruction algorithm,the accuracy of non-contact temperature measurement is affected,and it can not even be used.And in order to get the exact temperature in a particular area of the furnace and understand the status of the partial combustion inside the furnace,it is necessary to develop a set of temperature measuring devices on the basis of the principle of direct contact,which not only meet the demand of the contactless temperature measurement in situ calibration,and to monitor the fuel combustion and pollutants generated in the chamber of a stove or furnace condition,for judgement,prediction and diagnosis of boiler combustion state is of great significance.Therefore,in view of the requirements of high temperature flue gas temperature detection in the furnace,this paper focuses on the two key technical issues of temperature and atmosphere influence in the furnace.On the basis of summarizing the relevant temperature measurement technology at home and abroad,the thermal balance analysis of flue gas and thermocouple contact is first completed by theoretical analysis method.At the same time,in turn,on the basis of the principle of heat transfer,heat transfer control for radiation heat transfer,convection heat transfer and heat transfer heat transfer strengthen or weaken the corresponding measures were taken respectively,then the built-in function on the basis of the mathematical software Matlab to theory to explore the technical measures,analyzes the mask layer with the flue gas temperature change law of measurement error,The measurement error can be effectively reduced by increasing the number of heat shielding layers,and the nonlinear relationship between the increase of heat shielding layers and the decrease of measurement error is obtained.The requirement of measurement error can be satisfied if the number of heat shielding layers is greater than or equal to two layers.At the same time,the primary design of multi-channel exhaust temperature measuring device or a collaborative measuring method of high temperature flue gas temperature and composition in the furnace is presented.Secondly,in view of the multi-channel suction type temperature measuring device is the key temperature measuring parts of multi-channel flue gas flow structure geometry model,adopt the method of CFD numerical simulation,build the multi-channel flue gas flow structure model,has carried on the preliminary design of covering heat shield layer and device,the relationship between temperature measurement error and explore the block structure and covering hot heat shields shield blackness influence on measurement error,It is concluded that the measurement error can be effectively reduced by increasing the fin-like surface of the outer wall of the heat shield or reducing the blackness of the inner wall.The influence of non-constant velocity flow of flue gas on the temperature measurement error is explored,and the necessity of constant velocity sampling for temperature measurement is determined.It is pointed out that the measurement error after using constant velocity sampling meets the measurement error requirements in this paper.Explores the coal ash particles in flue gas,such as dispersed phase particles to the influence of the temperature measurement error,has been clear about the change with smoke particle size and particle radiation measurement error and the change rule of particle impact effect,explores the flue gas composition on the influence of the temperature measurement error,came to a similar this kind of symmetric structure of flue gas oxygen or nitrogen molecules for the thermal radiation of transparent medium,It can be regarded as a fluid-carrying gas molecule that has no effect on temperature measurement error,while it can be concluded that the asymmetrical structure of flue gas molecules such as carbon dioxide or water vapor has a greater effect on temperature measurement error.Finally,based on the influence degree of heat shield,flow rate,flue gas characteristics and other factors on the measurement error of the device,this paper completed the structure optimization,size finalization and manufacturing process,and carried out experimental verification results to meet the error requirements.Therefore,the development of a set of temperature measuring device based on multi-channel pumping is completed or a high temperature measuring method is put forward,which can accurately obtain the exact temperature in a specific area of the furnace and understand the local combustion condition of the furnace,and solve the problem that the temperature measurement error is not high in the high temperature flue gas environment in the furnace. |
